1. Field of the Invention
The present invention relates to a method of removing from tap water hypochlorous acid components that smell of chlorine, and a tap water processing apparatus for effectively processing tap water, including the removal of hypochlorous acid components.
2. Description of the Prior Art
Sources of tap water are freshwater rivers, lakes, swamps, artificial dams, reservoirs, etc. To purify the source water, a water purification plant guides the source water to a sand basin and a filter bed to remove suspended substances, bacteria, iron, manganese, organic substances that smell, etc., from the source water. Even after the removal of these substance, however the water is still active in terms of biochemistry and contains microbes and bacteria. The water must be disinfected, therefore, by adding chlorine thereto. Since river water etc. is very contaminated these days, a large amount of chlorine is frequently used for disinfection.
Article 16 of enforcement regulations of the Japanese City Water Law prescribes that tap water must contain residual chlorine, particularly residual hypochlorous acid. Thus, tap water supplied to homes always contains residual chlorine. In addition, this tap water usually contains trihalomethane, etc., produced by reaction of chlorine with organic substances. Among the residual substances, the chlorine smells bad, and if water contains a large quantity of residual chlorine, the taste of the water is poor.
To remove the residual chlorine, particularly hypochlorous acid that mainly smells bad, from tap water, it is usual to rely on an adsorbing process of a purifier that employs powdered activated carbon, granulated activated carbon, ion-exchange resins, etc., or a volatilizing process such as a bubbling process or a boiling process.
According to the bubbling process, an air pump feeds air into tap water to produce air bubbles in the water. The bubbles contact the hypochlorous acid to cause chemical decomposition, volatilizing and scattering, thereby removing the hypochlorous acid from the tap water.
According to the volatilizing process, tap water of usually 10.degree. to 20.degree. C. is heated to about 100.degree. C. This heated state is maintained until hypochlorous acid components are removed from the tap water. Thereafter, the water is cooled and used for drinking.
The adsorbing process removes hypochlorous acid from tap water with the help of activated carbon or ion-exchange resins. The adsorptive saturation quantity of this process is usually insufficient, or catalytic poison produced by the chemical adsorption of hypochlorous acid quickly deteriorates the adsorptive capacity of the activated carbon or the ion-exchange resin. Water purified in the purification plant or water purified by a volatile component removing method (disclosed in Japanese Laid-open Patent Publication No. 57-204285) still contains various organic substances. The activated carbon or the ion-exchange resin of the adsorbing process also adsorbs these substances, thereby lowering the efficiency of adsorbing hypochlorous acid.
The bubbling method is very costly because it employs an air pump that consumes a large amount of electric power and has a low removing efficiency.
The boiling method requires a boiling process and, therefore, consumes a large amount of energy, thereby increasing processing costs.